Load Bearing - Building & Construction - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction


Thread Tools Display Modes
Old 01-25-2014, 01:42 PM   #1
Join Date: Jan 2014
Posts: 1
Rewards Points: 10

load bearing

How much weight (at the middle) will an 11 ' douglas fir 4X4 carry? Supported at the ends.


GLK is offline   Reply With Quote
Old 01-25-2014, 10:44 PM   #2
Residential Designer
AndyGump's Avatar
Join Date: Sep 2010
Location: Orange County CA.
Posts: 1,386
Rewards Points: 688
Send a message via Skype™ to AndyGump

Maybe one child on a swing.



Residential Drafter/Designer
AndyGump is offline   Reply With Quote
Old 01-26-2014, 08:32 AM   #3
Join Date: Apr 2012
Location: UK
Posts: 714
Rewards Points: 502

Depends how much deflection you are prepared to tolerate.
tony.g is offline   Reply With Quote
Old 01-26-2014, 09:12 AM   #4
Civil Engineer
Join Date: Mar 2009
Location: Boston
Posts: 5,641
Rewards Points: 4,862

According the the Forestry Forum (http://www.forestryforum.com/members/donp/Fblist.htm), douglas fir has an allowable maximum fiber bending stress ranging from 875 psi for #2 to 1850 psi for dense select structural. Let's take the worst and the best case for you. Assume that your 4x4 is actually 3.5 inches by 3.5 inches.

Worst Case 875psi: 190 lbs at the midpoint
Best case 1850 psi: 400 lbs

These values provide a factor of safety of 1.0 in bending. This does NOT analyze for deflection, which may be important in your case. This does NOT analyze for shear, which may be important. This analyzes for a STATIC load only, does NOT account for dynamic loads such as a swinging load. This does NOT account for repetitive loading or fatigue, which may be important in your case.
Daniel Holzman is offline   Reply With Quote
The Following User Says Thank You to Daniel Holzman For This Useful Post:
Old 01-28-2014, 07:53 AM   #5
General Contractor
Gary Evans's Avatar
Join Date: Jan 2014
Location: B.C. - Canada
Posts: 110
Rewards Points: 75

Those are some good numbers Daniel.......good to know.

What's important to GLK is the weight this will support at mid span..........I'd stick to the lower half...........200 - 300 lbs.
Provided there's not a big knot anywhere near the mid span, which could weaken the 4x4 a lot.
If this is a dynamic load ( a swing for instance) what's your best guess Daniel for reducing that weight rating ?

Also I think deflection is more of a concern than shear.......providing there's proper bearing support at the ends.......at least 2" .......3" would be better.

Last edited by Gary Evans; 01-28-2014 at 07:57 AM.
Gary Evans is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Beam for Load Bearing Wall jstein69 Building & Construction 3 02-17-2012 05:26 PM
Removing Kitchen Soffit - load bearing?? adrien2 Carpentry 4 09-25-2011 06:29 PM
Determining a Load Bearing Wall (Pic Included) Evil Scotsman General DIY Discussions 18 03-02-2011 02:46 PM
Can't tell what to do with this wall, load bearing?? fox_forma Building & Construction 22 09-26-2009 05:31 PM
Load bearing wall in basement Ezekiel Building & Construction 3 11-12-2008 09:23 PM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1